I worked at SpaceX from 2010 to 2013, first doing software development on our manufacturing operations system, then later on on our telemetry/time-series platform. I think I averaged between 60 to 70 hours a week, which includes weekends if we need to support test or launch activities. In retrospect, that seems like a lot of hours, but it didn't feel like it because the work and the mission of the company is so inspiring. Elon was the final interviewer when I joined (I don't think he is doing that anymore) and he was explicit that working at SpaceX takes a different level of commitment.